This invention relates generally to an electrical connector and, more particularly, to a conductive elastomer connector and to the method of making the same.
U.S. Pat. Nos. 4,050,756 and 4,064,623 to Moore, assigned to the assignee of the present application, disclose a conductive elastomer connector and a method of making the same of which the present invention constitutes an improvement. More specifically, the Moore patents disclose a conductive elastomer connector comprising a plastic substrate, such as Mylar oriented polyester, having a plurality of etched holes therein, conductive elastomer rods are mounted in the holes and are retained therein by the underetch pattern which is used by the etched holes. The rods extend above the upper surface and below the lower surface of the substrate so that only the rods need be engaged in order to provide an electrical conductive path through the connector. As explained in the Moore patents, such connector may be made in extremely small sizes with a very close center-to-center spacing of the conductive elastomer rods. In accordance with the Moore method, a laminate is formed consisting of a plastic substrate having metal layers on the top and bottom surfaces thereof. Aligned holes are formed in the metal layers by etching using a standard photo-resist technique. Using the two-sided metal etched hole pattern as a template, the plastic substrate is then etched to provide holes therein aligned with the holes in the metal layers. The aligned holes are then filled with conductive elastomer to form conductive elastomer rods. Thereafter, the metal layers are removed from the plastic substrate leaving the conductive rods retained in the substrate which extend above and below the top and bottom surfaces thereof.
As disclosed in the Moore patents, the connector has been constructed utilizing a 0.003 inch Mylar substrate containing 15,625 conductive elastomer rods of 4-5 mils in diameter packaged into one square inch using 8 mils center-to-center spacing. Making the connector of such small size, with a highly dense pattern of conductive rods, is difficult and the connector has a few short-comings. More specifically, it is difficult to fabricate the substrate with a uniform hole pattern for mounting the conductive rods in a connector of the size contemplated in the Moore patents. That is to say, it is difficult to etch holes of accurate size and location in a plastic or other dielectric substrate. As a result, it is difficult to accurately reproduce the hole patterns in dielectric substrates with very close center-to-center spacing of the holes to enable production of a plurality of connectors with identical patterns of conductive elastomer rods. Also, because of the high coefficient of thermal expansion of a dielectric substrate, the substrate suffers dimension drift in response to temperature changes. That is, the size of the dielectric substrate will vary in response to temperature changes with results in variations in the pattern of the conductive elastomer rods with the consequence that there may be caused misalignment of the rods with traces on the mating electronic components interconnected by the connector.
It is the purpose of the present invention to provide a novel conductive elastomer connector arrangement and method of making the same which overcomes the aforementioned problems inherent in the prior art connector when made in very small sizes.